The characteristics of a battery using a metal fluoride as an active material include, for example, utilization of a conversion reaction. As such a battery, there is known, for example, a lithium ion battery where the cation in the electrolytic solution is Li+. A lithium ion battery utilizing a conversion reaction can have a capacity of, for example, from 2 to 3 times that of a lithium ion battery utilizing a normal insertion reaction (e.g., Non-Patent Document 1).